STR441 - what isit?

[Mike Watterson]

loads of Lockfits. BC147-BC149 and BF194-BF197. They have reliabilty problems in service. I wonder if they also fail in storage.

I'm convinced the issue is poor PCB design/insertion stressing the leads/package as the failures are:
a) Generally open or intermittent open circuit.
b) Only on certain models.

Clue in the name! A more exact PCB layout and thickness was needed.

It's the same chip, in most cases, as the earlier TO-18 metal can and later TO-92 plastic package. The leads are short, stiff, broad and ridged and it's designed to be a click fit without bending the lead-out or requiring force. Some of the PCBs I've seen certainly do not match the recommendations. Like the resistors with short ridged pins, the need for that type of insertion was short lived and replaced by TO-92 on bandoliers.
The differences of the BC series
xx7: higher voltage
xx8: general purpose AF amp or switching
xx9: higher gain which makes it seem lower noise, or maybe lower noise?
Also graded A, B, C in gain bands.
Then there are the PNP complements. There are 2N series JEDEC in the TO-18 and TO-92 but not lockfit.

I know less about the RF types (BF series), except they also are in three packages, there are 2N series JEDEC in the TO-18 and TO-92 but not lockfit and capacitances and fT is more important than gain or voltage.

"BD244, a perfectly sensible medium power PNP: http://www.radiotechnika.hu/images/BD244.pdf Oddly, the data sheet makes no mention of Ft or switching speed. "
Often not much of interest on Audio out stages. Often 4MHz down to 1MHz (higher power devices).